1. Field of the Invention
Example embodiments relate to a photolithography technique. More particularly, example embodiments relate to a method of correcting a critical dimension (CD) in a photomask and a photomask having a CD corrected using the method.
2. Description of the Related Art
Generally, a photomask refers to a high-precision plate used to form an integrated circuit (IC) on a wafer. Such a photomask may include a transparent substrate and a shielding pattern formed on one surface of the transparent substrate. Generally, the shielding pattern in the photomask defines a circuit pattern. For example, the shielding pattern may be a photoresist pattern used to form a circuit pattern on a substrate. Theoretically, a critical dimension (CD) of the shielding pattern of the photomask and a CD of the corresponding circuit pattern formed on the wafer should be identical to each other. However, for reasons including space distribution defects of an exposure source, defects of exposure equipment such as lens defects, errors of the shielding pattern of the photomask, etc.; the CD of the shielding pattern and the CD of the circuit pattern may be different from each other.
Conventionally, correcting a CD of a photomask may include a method of etching a transparent substrate adjacent to a shielding pattern of the photomask by a desired and/or predetermined depth or a method of forming a diffraction grating on a rear surface of a transparent substrate in which a shielding pattern is not formed.
However, both the conventional method of etching the transparent substrate and the conventional method of forming the diffraction grating require etching a substrate in a photomask by a desired and/or predetermined depth, so as to precisely correct CDs of shielding patterns. Conventional techniques for precisely etching the substrate may be difficult, costly and/or lead to defects.